   on the server. Defaults to filling in the full buffer unless start and
   len vals are specified. Asynchronous."
   ([buf val]
+     (ensure-buffer-active! buf)
      (assert (buffer? buf))
      (buffer-fill! buf 0 (:size buf) val))
   ([buf start len val]

  "Read a single value from a buffer. Index defaults to 0 if not specified."
  ([buf] (buffer-get buf 0))
  ([buf index]
     (assert (buffer? buf))
     (let [buf-id (:id buf)
           prom   (recv "/b_set" (fn [msg]

  the server. Index defaults to 0 if not specified."
  ([buf val] (buffer-set! buf 0 val))
  ([buf index val]
     (ensure-buffer-active! buf)
     (assert (buffer? buf))
     (snd "/b_set" (:id buf) index (double val))
     buf))
